This story from a couple weeks back also provides more info (via Crains):

Nearly two years after a developer first offered to buy all the condos at River City in the South Loop, the homeowners association finally has enough votes to sell, but just barely.

The $100 million sale of River City's 448 condos would be the biggest Chicago condo development by far to switch to rentals in the recent wave of deconversions.

The next-largest sale by condo owners for conversion to rental entailed convincing less than half as many different owners: Last spring, owners in the 207-unit building at 420 W. Belmont Ave. approved a developer's $51.5 million offer.

After a series of delays during the fall when the votes in favor hadn't quite reached the 75 percent that Illinois condo law requires, the River City Condominium Association announced in an email to River City owners last week that owners of 75.87 percent of the River City complex now support selling.

It's still amazing to us that there is this much demand for apartments...